Tavily Web Search MCP Server

Instructions

Implementation Reference

• server.py:21-25 (handler)

  The main handler function for the 'roll_dice' MCP tool, decorated with @mcp.tool() which registers it with the FastMCP server. It instantiates DiceRoller and returns its string representation containing the roll results.

  @mcp.tool()
  def roll_dice(notation: str, num_rolls: int = 1) -> str:
      """Roll the dice with the given notation"""
      roller = DiceRoller(notation, num_rolls)
      return str(roller)

• dice_roller.py:10-23 (helper)

  Core implementation of dice rolling logic within DiceRoller class: parses dice notation (e.g., '2d6k1'), generates random rolls, sorts descending, keeps top N rolls, and returns all rolls and kept rolls.

  def roll_dice(self):
      match = self.dice_pattern.match(self.notation)
      if not match:
          raise ValueError("Invalid dice notation")
  
      num_dice = int(match.group(1))
      dice_sides = int(match.group(2))
      keep = int(match.group(4)) if match.group(4) else num_dice
  
      rolls = [random.randint(1, dice_sides) for _ in range(num_dice)]
      rolls.sort(reverse=True)
      kept_rolls = rolls[:keep]
  
      return rolls, kept_rolls

• dice_roller.py:37-47 (helper)

  __str__ method of DiceRoller that formats the output string returned by the tool handler. Handles single or multiple rolls, calling roll_dice() or roll_multiple().

  def __str__(self):
      if self.num_rolls == 1:
          rolls, kept_rolls = self.roll_dice()
          return f"ROLLS: {', '.join(map(str, rolls))} -> RETURNS: {sum(kept_rolls)}"
      else:
          results = self.roll_multiple()
          result_strs = []
          for i, result in enumerate(results, 1):
              result_strs.append(f"Roll {i}: ROLLS: {', '.join(map(str, result['rolls']))} -> RETURNS: {result['total']}")
          return "\n".join(result_strs)

• dice_roller.py:4-9 (helper)

  DiceRoller class initialization, storing notation and num_rolls, compiling regex for parsing dice notation supporting 'NdSk' format.

  class DiceRoller:
      def __init__(self, notation, num_rolls=1):
          self.notation = notation
          self.num_rolls = num_rolls
          self.dice_pattern = re.compile(r"(\d+)d(\d+)(k(\d+))?")